Substantial numbers of people are diagnosed every year with kidney stones and gall stones, termed renal and biliary calculi. Heretofore, painful surgery or lengthy drug therapy were the only known methods of treating such calculi. Recently, ESWL has become an accepted method of noninvasively treating human calculi.
The ESWL procedure used to fragment kidney stones and gall stones is well known. An ultrasonic or X-ray locating device is employed to pinpoint the exact location of a calculus found in the kidney or gall bladder. After the stone is located, a physician or technician trained in the use of an ESWL apparatus focuses the shock wave of the apparatus at the calculus and triggers a focussed shock wave. The calculus is destroyed by fragmentation in response to the shock wave, and the particles of the calculus, being substantially reduced in size, are typically passed through the bile ducts or urethra without substantial harm or pain.
It is extremely important that the physician or technician be able to accurately locate a calculus and correctly focus the shock wave on a located calculus. If the shock waves are not focussed correctly, complications can arise such as damage to other tissues or organs in the patient's body, and the need for application of additional shock wave therapy (which is not a completely painless procedure) to complete the destruction of the calculus. Therefore, there is a need for efficient and accurate tools for training physicians and technicians in the location of calculi, ESWL focussing, and application of an ESWL shock wave to the located calculi in a harmless training environment, to facilitate the efficient and safe location of gall stones and kidney stones in live patients with reduced risk of error and harm to the patient, or without excessive application of shock wave therapy.
One known device used for training technicians in ultrasound techniques is described in the article entitled "Anthropomorphic Torso Section Phantom for Ultrasonic Imaging" by Madsen et al. This article describes a torso section phantom for use as a training aid for ultrasonic technicians or as a tool in the development of more sophisticated ultrasound scanners. The Madsen et al. phantom comprises a tissue equivalent kidney, a tissue equivalent fat pad surrounding the kidney, a tissue equivalent aorta, tissue equivalent tumors, bowel gas, ribs, a spine, and resolution fibers. The remainder of the phantom is filled with a tissue equivalent liver material. All tissue types represented in the phantom are mimicked with respect to the attenuation coefficient, density, and the speed of sound. The tissue equivalent aortic blood, cysts, and tumors are molded around stainless steel wire and suspended in the phantom before the tissue equivalent liver material is poured. After the tissue equivalent liver material is poured and congealed, the suspending wires are withdrawn, thereby forming voids representing blood, cysts, and tumors in the phantom.
It was a requirement of the Madsen et al. phantom that the shape of the objects possess considerable geometric simplicity, mainly for the purpose of demonstrating and explaining scanning artifacts related either to discontinuities in density and/or speed of sound at smooth organ boundaries or to variations in the average speed of sound over pulse echo paths. Thus, none of the organs or shapes within this phantom are constructed to anatomically exactly resemble their human counterparts. Nor is any means provided for introducing a real or simulated calculus into a simulated organ for imaging. Consequently, an ultrasound technician will not see the actual shape of organs or calculi found in the human body when viewing the interior of the phantom.
Moreover, the Madsen et al. phantom is not constructed of a material suitable for being subjected to repetitive shock wave impulses, nor is it constructed in a manner so as to allow placement of calculi for location and actual destruction using ESWL. Because of these and other limitations, the Madsen et al. phantom is not suitable for use as a teaching and training aid for ultrasonic location and ESWL destruction of renal and biliary calculi.
Another phantom is described in U.S. Pat. No. 4,493,653 to Robbins. This patent describes a biopsiable ultrasound phantom for training technicians to ultrasonically locate a cyst, then perform an actual biopsy on the located cyst in the phantom. A plurality of small balloons filled with a viscous substance are provided for mimicking cysts. The balloons are suspended with nylon threads and then hung in a box. The box is then filled with a gelatinous substance comprising tissue eqivalent material. After the material has set, an ultrasonic scanner is placed against the top surface of the phantom and a technician locates a "cyst". Using the image provided by the ultrasonic scanner, the technician guides a biopsy needle into the located cyst, then aspirates the viscous substance from the cyst.
However, the Robbins phantom is also not an effective teaching and training aid for the ultrasonic location of calculi and simulated ESWL application because it has a finite number of cysts. No means are provided for introducing a calculus. When all the cysts have been aspirated, the usefulness of this phantom has ended and a new phantom must be constructed. Moreover, each of the plurality of cysts is the same, and the phantom is not constructed anthropomorphically so that the ultrasonic images substantially comport with the appearance of an actual human patient.
There is accordingly a need for a method and apparatus which can train physicians and technicians in the combination of medical imaging and ESWL techniques. There is also a need for an apparatus which can duplicate the size, shape and position of organs found within the human body. There is a further need for an ultrasound and ESWL training and teaching apparatus which can be used an inexhaustible number of times.